Alpine Linux:Overview: Difference between revisions

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When I discovered Alpine, I had a hard time figuring out what did what. Part of the trouble is that, as the [http://alpinelinux.org/about About] page says:
Alpine uses [https://musl.libc.org/ musl] as its libc, and [[BusyBox]] as core utilities. These choices tend to make Alpine especially minimalist and secure.


<blockquote>
== General overview ==
* In some cases, there is not a lot of documentation available, and what is available can be scattered about the wiki and/or mailing lists. We're working on it, but could use some help. Please see the [[Contribute]] page if you would like to help out.
</blockquote>


Another part of the trouble is that up-to-date information in the wiki was mixed together with information that only concerned older versions of Alpine (and sometimes it wasn't clear when that was true). I've tried to clean up such things when I've encountered them.
Alpine Linux has one of the '''fastest boot times''' of any operating system.


A third part of the trouble is that there's too little by way of a global overview of the distro, or its development tools. This page is aimed at remedying that.
It's famous because of its small size and it's '''heavily used in containers'''.


== Overview ==
It's also well known for '''wide use in embedded devices''' and as a '''base system for many enterprise routers'''.


There are four areas that distinguish Linux distros from each other.
The postmarketOS project, which is designed to run on mobile devices, is based on Alpine Linux.
 
=== Distinctive ===
 
Alpine Linux follows the principles of '''the SSS distro: Simple+Small+Secure''': due to usage of [https://musl.libc.org/ muslc] as the minimalist libc, BusyBox simple coreutils (with possibilities to alternate on inflated original packages of each coreutils tools also) and userland binaries compiled as Position Independent Executables (PIE) with stack smashing protection.
 
=== Efficient ===
 
Some main reasons:
 
# Usage of [https://musl.libc.org/ musl] as the minimalist libc
# Its own package manager called [[Alpine Package Keeper|apk]],
# The {{Pkg|openrc}} init system, script driven set-ups and that’s it!
# {{Pkg|busybox}}: simple coreutils (with possibilities to alternate on inflated original packages of each coreutils tools also)
 
This provides you with a simple, '''crystal-clear Linux environment without all the noise''', nothing else will get in the way.
 
=== Secure ===
 
All userland binaries are compiled as Position Independent Executables (PIE) with stack smashing protection.
 
== Technical overview ==


<ol>
<ol>
<li>The initial design choices
<li>'''Architectures'''
 
<p>Alpine uses '''Linux''' as [https://www.kernel.org/ OS kernel], and has a focus on '''SSS distribution, Simple Small and Secure'''</p>
 
<p>A variety of architectures are officially supported:
* '''x86_64''': The popular AMD64 compatible 64-bit x86 based machines, i386 are not recommended for newer/latest hardware.
* '''x86''': (i386 pc 32bit) and x86_64 (i686 pc 64bit and amd64)
* '''armhf''': The newer ARM hard-float for newer, more powerful 32-bit devices alongside 64-bit
* '''armv7''': The 32-bit ARM only execution state of the ARMv7 devices machines.
* '''aarch64''': The 64-bit ARM only execution state of the ARMv8 device machines.
* '''ppc64le''': For 64-bit PowerPC devices with pure little-endian mode, mostly for POWER8 and POWER9.
* '''s390x''': For IBM Z mainframes, especially IBM Z and IBM LinuxONE.


<p>What makes Alpine distinctive is summarized on the [http://alpinelinux.org/about About] page. This includes applying the [https://en.wikipedia.org/wiki/Grsecurity grsec]/PaX patches to the kernel (though you can also compile and use a custom kernel, configured as you like). It also includes the choice of [https://en.wikipedia.org/wiki/UClibc uClibc], and [https://en.wikipedia.org/wiki/BusyBox BusyBox] for the core utilities. These choices tend to make Alpine especially minimalist and secure: as the About page says, it's "designed for x86 Routers, Firewalls, VPNs, VoIP and servers." (Alpine is a perfectly workable desktop system, too. The shortcomings just have to do with the small community, and that sometimes you may need to get your hands dirty modifying scripts written with more mainstream desktop distros in mind. So you probably won't want to use Alpine if you're a newcomer to Linux. If you're already comfortable with another distro, though, especially a power-user, less-hand-holding distro like [https://www.archlinux.org/ ArchLinux] or [http://www.gentoo.org/ Gentoo], you should do fine.)


</p><p>Another distinctive part of Alpine is its variety of "installation modes." It can be installed to a hard disk/SSD/other storage medium like any other distro; this is called the '''sys''' mode. The storage medium in question can be removable, if you like, so long as you can configure your machine to boot from it. However, if you're working with removable media, there are two other installation modes you might consider. In each of these modes, you will boot your machine from a static ISO image (either a CD or a USB partition configured like the CD). You will also need a writable medium to save updates to the system. In the '''diskless''' mode, this writable medium is typically a small USB key (or a second USB partition) that holds the changes you want to persist. Both the base Alpine system and all your changes will be unpacked into a memory-based filesystem. The other, '''data''' mode is for cases where you're dealing with a large amount of persisting data, that you want to keep on a hard disk/SSD/other storage medium, rather than unpacking into memory. The default setup here is to store your {{Path|/var}} partition directly on the hard storage medium. But as in the '''diskless''' mode, your root system still comes from a static ISO image.
</li><li>'''Installing'''


</p><p>Key to the second and third modes is Alpine's [[Alpine local backup|lbu]] utility. This tracks which files you've modified from their static ISO version, and want the changes to persist. The lbu utility saves those changes in {{Path|.apkovl}} "overlay" files (these are essentially tar-gzip archives, though they can also be encrypted).
<p>Alpine can be installed to a hard disk/SSD/other storage medium like any other distro (this is called '''sys mode'''). The storage medium in question can be any block device (USB, Flash, SDD, HDD). It can be removable, so long as you can configure your machine to boot from it. But if you're working with removable media, you might prefer one of the other installation modes.</p>
You can use the lbu utility with the '''sys''' mode, too, if you like: as a form of backup, or to configure overlay files for other systems. But for a robust incremental backup system, you'll probably want a more specialized tool. (Such as [http://www.rsnapshot.org/ rsnapshot], which is a perl wrapper around {{Pkg|rsync}}.)


</p><p>The lbu utility is part of the {{Pkg|alpine-conf}} package, which is required by {{Pkg|alpine-base}}.
<p>In each of these modes, you boot your machine from a static image. You will also need a writable medium to save updates to the system. In '''diskless mode''', that medium is usually a small USB key (or a partition on one) that holds the changes you want to persist. Both the base Alpine system and all your changes will be unpacked into a memory-based filesystem.</p>


</p><p>Another distinctive part of a Linux distro is its default bootloader. In Alpine's case this is {{Pkg|syslinux}}, or its companions <code>isolinux</code> or <code>extlinux</code>.
<p>The other, '''data''' mode is for when you're dealing with a large amount of persisting data, that you want to keep on a hard disk/SSD/other storage medium, rather than unpacking into memory. The default setup here is to store your {{Path|/var}} partition directly on the hard storage medium. But as in the '''diskless''' mode, your root system still comes from a static ISO image.</p>
</p>


</li><li>The installer scripts
<p>These second and third installation modes are sometimes referred to, collectively, as "run-from-RAM" installations.</p>


<p>In Alpine's case, the installer consists of the {{Path|/sbin/setup-*}} scripts, which are also part of the {{Pkg|alpine-conf}} package.
<p>Key to these installation modes is Alpine's [[Alpine local backup|lbu]] utility. This tracks which files you've modified from their static ISO version, and want the changes to persist. The lbu utility saves those changes in {{Path|.apkovl}} "overlay" files. (These are essentially tar-gzip archives, though they can also be encrypted. You can use the lbu utility with the '''sys''' mode, too, if you like: as a form of backup, or to configure overlay files for other systems. But for a robust incremental backup system, you'll probably want a more specialized tool, such as {{Pkg|rsnapshot}}.)</p>


</p><p>A base Alpine install will include only these packages and their dependencies:
<p>The lbu utility is part of the {{Pkg|alpine-conf}} package, which is required by {{Pkg|alpine-base}}.</p>


* {{Pkg|alpine-base}}
* {{Pkg|syslinux}}
* {{Pkg|linux-grsec}} or another kernel package


</p><p>Depending on your installation choices, you may also have:
<p>'''Alpine's installer''' consists of '''the {{Path|/sbin/setup-*}} scripts''', which are also part of the {{Pkg|alpine-conf}} package.


* {{Pkg|openssh}}
</p><p>'''A base Alpine install will include only needed packages''' such like {{Pkg|alpine-base}}, {{Pkg|syslinux}}, {{Pkg|linux-lts}} (or another kernel package), and depending on your purposes packages like {{Pkg|openssh}} and/or {{Pkg|chrony}}.
* {{Pkg|chrony}}


</p><p>or other such packages. <!-- e2fsprogs? --> Everything else is up to you to install.
</p><p>Alpine's boot loader in that case is {{Pkg|syslinux}}, or its companions <code>isolinux</code> or <code>extlinux</code>. The latest releases also have Grub and [[Alpine and UEFI|UEFI support]].</p>
</p>


</li><li>The init system
</li><li>'''The init system'''


<p>An "init system" includes several different components. First, there is the initramfs loaded by the bootloader. Alpine's tool for generating these is {{Path|/sbin/mkinitfs}}, part of the {{Pkg|mkinitfs}} package, which is required by Alpine's kernel packages and by its {{Pkg|syslinux}} package. This tool's settings are read from {{Path|/etc/mkinitfs/*}}, and it installs the initscript {{Path|/usr/share/mkinitfs/initramfs-init}} into the initramfs.
<p>An "init system" includes several different components. First, there is the initramfs, which is loaded by the bootloader. Alpine's tool for generating the initramfs is {{Path|/sbin/mkinitfs}}, part of the {{Pkg|mkinitfs}} package, which is required by Alpine's kernel packages and by its {{Pkg|syslinux}} package. This tool's settings are read from {{Path|/etc/mkinitfs/*}}, and it installs the initscript {{Path|/usr/share/mkinitfs/initramfs-init}} into the initramfs.


</p><p>Second, Alpine uses [[Alpine Linux Init System|OpenRC]] to handle the rest of its initscripts. The base framework of this is in the {{Pkg|openrc}} package, which is required by {{Pkg|alpine-conf}}.
</p><p>Second, Alpine uses [[Alpine Linux Init System|OpenRC]] to handle the rest of its initscripts. The base framework of this is in the {{Pkg|openrc}} package, which is required by {{Pkg|alpine-conf}}.
</p>
</p>


</li><li>The packaging and development systems
</li><li>'''The packaging and development system'''


<p>The last important distinguishing feature of a Linux distro is its packaging and development systems.
<p>The last important distinguishing feature of a Linux distro is its packaging and development systems.


</p><p>In Alpine's case, these are something a hybrid between [https://www.archlinux.org/ ArchLinux]'s, on the one hand, and [http://www.gentoo.org/ Gentoo] and [http://www.freebsd.org/ FreeBSD]'s, on the other. Our package-management and build utilities work much like Arch's:
</p><p>In Alpine's case, these are something a hybrid between [https://www.archlinux.org/ ArchLinux]'s, on the one hand, and [https://www.gentoo.org/ Gentoo] and [https://www.freebsd.org/ FreeBSD]'s, on the other. Our package-management and build utilities work much like Arch's:


* {{Pkg|mkinitfs}}, mentioned above, rebuilds Alpine's initramfs, like Arch's "mkinitcpio"
* {{Pkg|mkinitfs}}, mentioned above, rebuilds Alpine's initramfs, like Arch's "mkinitcpio"
Line 64: Line 86:
* Alpine's package-building scripts are named APKBUILD, like Arch's "PKGBUILD"
* Alpine's package-building scripts are named APKBUILD, like Arch's "PKGBUILD"


</p><p>What Alpine borrows from Gentoo and FreeBSD is a tree of all the package-building scripts. We call this our [[Aports tree]], and we keep it as a git repository. (Compare Gentoo's "Portage" and FreeBSD's "ports". You can setup something similar with Arch's "abs", but it's not as tightly integrated with their package manager and build utilities.)
</p><p>What Alpine borrows from Gentoo and FreeBSD is a tree of all the package-building scripts. It is called the [[Aports tree]], and is kept as a single git repository. (Compare Gentoo's "Portage" and FreeBSD's "ports". Something similar can be set up with Arch's "abs", but it's not as tightly integrated with their package manager and build utilities.)


</p><p>If you're only planning to install packages on a given system, and not do any development there, then the only pieces of this you'll need are {{Pkg|mkinitfs}} and {{Pkg|apk-tools}}, both included in a base Alpine install. If you do plan to do development, install {{Pkg|alpine-sdk}}, which includes gcc, git, abuild, and the like, and see [[Developer Documentation]].
</p><p>If you're only planning to install packages on a given system, and not do any development there, then the only pieces of this you'll need are {{Pkg|mkinitfs}} and {{Pkg|apk-tools}}, both included in a base Alpine install. If you do plan to do development, install {{Pkg|alpine-sdk}}, which includes gcc, git, abuild, and the like, and see [[Developer Documentation]].
Line 70: Line 92:


</li></ol>
</li></ol>
= See Also =
* [[Comparison with other distros]]
* [[Tutorials and Howtos]]
* [https://en.wikipedia.org/wiki/BusyBox BusyBox]
[[Category:Installation]]

Latest revision as of 13:31, 21 October 2024

Alpine uses musl as its libc, and BusyBox as core utilities. These choices tend to make Alpine especially minimalist and secure.

General overview

Alpine Linux has one of the fastest boot times of any operating system.

It's famous because of its small size and it's heavily used in containers.

It's also well known for wide use in embedded devices and as a base system for many enterprise routers.

The postmarketOS project, which is designed to run on mobile devices, is based on Alpine Linux.

Distinctive

Alpine Linux follows the principles of the SSS distro: Simple+Small+Secure: due to usage of muslc as the minimalist libc, BusyBox simple coreutils (with possibilities to alternate on inflated original packages of each coreutils tools also) and userland binaries compiled as Position Independent Executables (PIE) with stack smashing protection.

Efficient

Some main reasons:

  1. Usage of musl as the minimalist libc
  2. Its own package manager called apk,
  3. The openrc init system, script driven set-ups and that’s it!
  4. busybox: simple coreutils (with possibilities to alternate on inflated original packages of each coreutils tools also)

This provides you with a simple, crystal-clear Linux environment without all the noise, nothing else will get in the way.

Secure

All userland binaries are compiled as Position Independent Executables (PIE) with stack smashing protection.

Technical overview

  1. Architectures

    Alpine uses Linux as OS kernel, and has a focus on SSS distribution, Simple Small and Secure

    A variety of architectures are officially supported:

    • x86_64: The popular AMD64 compatible 64-bit x86 based machines, i386 are not recommended for newer/latest hardware.
    • x86: (i386 pc 32bit) and x86_64 (i686 pc 64bit and amd64)
    • armhf: The newer ARM hard-float for newer, more powerful 32-bit devices alongside 64-bit
    • armv7: The 32-bit ARM only execution state of the ARMv7 devices machines.
    • aarch64: The 64-bit ARM only execution state of the ARMv8 device machines.
    • ppc64le: For 64-bit PowerPC devices with pure little-endian mode, mostly for POWER8 and POWER9.
    • s390x: For IBM Z mainframes, especially IBM Z and IBM LinuxONE.
  2. Installing

    Alpine can be installed to a hard disk/SSD/other storage medium like any other distro (this is called sys mode). The storage medium in question can be any block device (USB, Flash, SDD, HDD). It can be removable, so long as you can configure your machine to boot from it. But if you're working with removable media, you might prefer one of the other installation modes.

    In each of these modes, you boot your machine from a static image. You will also need a writable medium to save updates to the system. In diskless mode, that medium is usually a small USB key (or a partition on one) that holds the changes you want to persist. Both the base Alpine system and all your changes will be unpacked into a memory-based filesystem.

    The other, data mode is for when you're dealing with a large amount of persisting data, that you want to keep on a hard disk/SSD/other storage medium, rather than unpacking into memory. The default setup here is to store your /var partition directly on the hard storage medium. But as in the diskless mode, your root system still comes from a static ISO image.

    These second and third installation modes are sometimes referred to, collectively, as "run-from-RAM" installations.

    Key to these installation modes is Alpine's lbu utility. This tracks which files you've modified from their static ISO version, and want the changes to persist. The lbu utility saves those changes in .apkovl "overlay" files. (These are essentially tar-gzip archives, though they can also be encrypted. You can use the lbu utility with the sys mode, too, if you like: as a form of backup, or to configure overlay files for other systems. But for a robust incremental backup system, you'll probably want a more specialized tool, such as rsnapshot.)

    The lbu utility is part of the alpine-conf package, which is required by alpine-base.


    Alpine's installer consists of the /sbin/setup-* scripts, which are also part of the alpine-conf package.

    A base Alpine install will include only needed packages such like alpine-base, syslinux, linux-lts (or another kernel package), and depending on your purposes packages like openssh and/or chrony.

    Alpine's boot loader in that case is syslinux, or its companions isolinux or extlinux. The latest releases also have Grub and UEFI support.

  3. The init system

    An "init system" includes several different components. First, there is the initramfs, which is loaded by the bootloader. Alpine's tool for generating the initramfs is /sbin/mkinitfs, part of the mkinitfs package, which is required by Alpine's kernel packages and by its syslinux package. This tool's settings are read from /etc/mkinitfs/*, and it installs the initscript /usr/share/mkinitfs/initramfs-init into the initramfs.

    Second, Alpine uses OpenRC to handle the rest of its initscripts. The base framework of this is in the openrc package, which is required by alpine-conf.

  4. The packaging and development system

    The last important distinguishing feature of a Linux distro is its packaging and development systems.

    In Alpine's case, these are something a hybrid between ArchLinux's, on the one hand, and Gentoo and FreeBSD's, on the other. Our package-management and build utilities work much like Arch's:

    What Alpine borrows from Gentoo and FreeBSD is a tree of all the package-building scripts. It is called the Aports tree, and is kept as a single git repository. (Compare Gentoo's "Portage" and FreeBSD's "ports". Something similar can be set up with Arch's "abs", but it's not as tightly integrated with their package manager and build utilities.)

    If you're only planning to install packages on a given system, and not do any development there, then the only pieces of this you'll need are mkinitfs and apk-tools, both included in a base Alpine install. If you do plan to do development, install alpine-sdk, which includes gcc, git, abuild, and the like, and see Developer Documentation.

See Also

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